Reconfigurable optical add/drop multiplexer having an array of micro-mirrors

• US 20030095307A1
• Filed: 09/25/2002
• Published: 05/22/2003
• Est. Priority Date: 09/25/2001
• Status: Abandoned Application

• Current Assignee: II-VI Delaware, Inc. (Coherent Corp.)
• Original Assignee: Cidra Sarl (Nordic Cultural & Educational Foundation)
• Inventors: Kersey, Alan D., Moon, John A., Dawson, Jay W., Dunphy, James R., Pinto, Joseph, Szczepanek, Paul, OʼKeefe, Christian
• Application Number:
  US10/255,141
• Publication Number:
  US 20030095307A1
• Time in Patent Office: Days
• US Class Current: 398/45
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 27/1006 for splitting or combining different wavelengths G02B27/1086, G02B27/141 take precedence
• CPC Class Codes: G02B 27/1086 operating by diffraction only
• CPC Class Codes: G02B 6/262 Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
• CPC Class Codes: G02B 6/2931 Diffractive element operating in reflection
• CPC Class Codes: G02B 6/29382 including at least adding or dropping a signal, i.e. passing the majority of signals
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: G02B 6/4226 Positioning means for moving the elements into alignment, e.g. alignment screws, deformation of the mount
• CPC Class Codes: H04J 14/0208 Interleaved arrangements
• CPC Class Codes: H04J 14/0209 Multi-stage arrangements, e.g. by cascading multiplexers or demultiplexers
• CPC Class Codes: H04J 14/021 Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM]
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04J 14/0213 Groups of channels or wave bands arrangements

Abstract

A reconfigurable optical add/drop multiplexer (ROADM) selectively drops and/or adds desired optical channel(s) from and/or to an optical WDM input signal. The ROADM includes a spatial light modulator having a micro-mirror device with an array of micro-mirrors, and a light dispersion element. The micro-mirrors tilt between two positions in response to a control signal provided by a controller in accordance with a switching algorithm and input command. Collimators, diffraction gratings and Fourier lens collectively collimate, separate and focus the optical input channels and optical add channels onto the array of micro-mirrors. Each optical channel is focused on micro-mirrors of the micro-mirror device, which effectively pixelates the optical channels. To drop and/or add an optical channel to the optical input signal, mirrors associated with each desired optical channel are tilted away from a return path to the second position.

Claims

1. A reconfigurable optical add/drop multiplexer comprising an optical arrangement for receiving an optical input signal and an optical add signal, each optical signal having one or more optical bands or channels, and including a spatial light modulator having a micro-mirror device with an array of micro-mirrors for reflecting the one or more optical signals provided thereon, wherein

the optical arrangement comprises a free optics configuration having at least one light dispersion element for separating the optical input signal and the optical add signal so that each optical band or channel is reflected by a respective plurality of micro-mirrors to selectively add or drop the one or more optical bands or channels to and/or from an optical input signal.

2. An optical add/drop multiplexer according to claim 1, wherein the one or more light dispersion elements include either a diffraction grating, an optical splitter, a holographic device, a prism, or a combination thereof.

3. An optical add/drop multiplexer according to claim 2, wherein the diffraction grating is a blank of polished fused silica or glass with a reflective coating having a plurality of grooves either etched, ruled or suitably formed thereon.

4. An optical add/drop multiplexer according to claim 2, wherein the diffraction grating is tilted and rotated approximately 90 degrees in relation to the spatial axis of the dispersed optical input signal.

5. An optical add/drop multiplexer according to claim 1, wherein the spatial light modulator is programmable for reconfiguring the optical add/drop multiplexer to drop and/or add a desired channel by changing a switching algorithm that drives the array of micro-mirrors.

6. An optical add/drop multiplexer according to claim 1, wherein the array of micro-mirrors includes a multiplicity of micro-mirrors that are separately controllable for tilting on an axis depending on a control signal in accordance with a switching algorithm.

7. An optical add/drop multiplexer according to claim 1, wherein the optical input signal is a wavelength division multiplexed (WDM) optical signal having a plurality of wavelengths and a corresponding plurality of optical bands or channels, each optical band or channel reflecting off a respective group of micro-mirrors of the micro-mirror device.

8. An optical add/drop multiplexer according to claim 5, wherein the spatial light modulator is selectively reconfigurable by statically or dynamically modifying the switching algorithm to accommodate different channel spacing, the shape of the light beam, or the center wavelength of the light beam of the optical input signal.

9. An optical add/drop multiplexer according to claim 5, wherein the switching algorithm is based on the wavelength of the optical input signal and the one or more optical channels being added or dropped.

10. An optical add/drop multiplexer according to claim 7, wherein the respective group of micro-mirrors are collectively tilted to reflect channels in either the optical input signal, at least one optical add signal to be added to the optical input signal, an optical output signal, at least one optical drop signal dropped from the optical input signal, or a combination thereof.

11. An optical add/drop multiplexer according to claim 1, wherein each micro-mirror is tiltable in either a first position or a second position along an axis either substantially parallel to the spectral axis of the optical input signal, parallel to the spatial axis of the optical input signal, or at an angle of 45 degrees in relation to the spatial axis.

12. An optical add/drop multiplexer according to claim 1, wherein the optical arrangement includes one or more optical portions that provide the optical input signal and the one or more optical signals to the spatial light modulator, and also provide an optical output signal having remaining optical channels after channels have been added and/or dropped and one or more optical signals dropped from the optical input signal from the spatial light modulator.

13. An optical add/drop multiplexer according to claim 12, wherein the one or more optical portions include either one or more circulators, one or more waveguides, or a combination thereof.

14. An optical add/drop multiplexer according to claim 13, wherein the one or more optical portions either receive the optical input signal or the one or more optical signals to be added to the optical input signal, provide the optical output signal or one or more optical signals dropped from the optical input signal, or a combination thereof.

15. An optical add/drop multiplexer according to claim 13, wherein the one or more circulators includes a pair of circulators.

16. An optical add/drop multiplexer according to claim 13, wherein the one or more waveguides includes a pair of capillary tubes.

17. An optical add/drop multiplexer according to claim 13, wherein the one or more circulators includes a three port circulator.

18. An optical add/drop multiplexer according to claim 12, wherein the one or more optical portions include a pair of optical portions, including one optical portion for providing the optical input signal and the one or more optical signals to be added to the optical input signal to the spatial light modulator, and another optical portion for providing the optical output signal and the one or more optical signals dropped from the optical input signal from the spatial light modulator.

19. An optical add/drop multiplexer according to claim 12, wherein the one or more optical portions includes three optical portions, including a first optical portion for providing the one or more optical signals to be added to the optical input signal to the spatial light modulator, a second optical portion for providing the optical input signal to the spatial light modulator, and for providing the one or more optical signals dropped from the optical input signal from the spatial light modulator, and a third optical portion for providing the optical output signal from the spatial light modulator.

20. An optical add/drop multiplexer according to claim 12, wherein the one or more optical portions include a collimator, a reflective surface, the dispersion element, a bulk lens, or a combination thereof.

21. An optical add/drop multiplexer according to claim 20, wherein the collimator includes either an aspherical lens, an achromatic lens, a doublet, a GRIN lens, a laser diode doublet, or a combination thereof.

22. An optical add/drop multiplexer according to claim 20, wherein the reflective surface includes a mirror.

23. An optical add/drop multiplexer according to claim 20, wherein the reflective surface is curved.

24. An optical add/drop multiplexer according to claim 20, wherein the bulk lens includes a Fourier lens.

25. An optical add/drop multiplexer according to claim 12, wherein the one or more optical portions provide either the optical input signal, the one or more optical signals to be added, or a combination thereof as different channels having different wavelengths on the spatial light modulator.

26. An optical add/drop multiplexer according to claim 25, wherein the different channels have a desired cross-sectional geometry, including elliptical, rectangular, square or polygonal.

27. An optical add/drop multiplexer according to claim 25, wherein the spatial light modulator is configured so one group of channels is spaced at 100 GHz and another group of channels is spaced at 50 GHz.

28. An optical add/drop multiplexer according to claim 12, wherein the one or more optical portions further comprise a further optical portion for receiving the optical input signals and the one or more channels to be added to the optical input signal from the spatial light modulator and providing these same optical signals back to the spatial light modulator, and for receiving the one or more optical signals dropped from the optical input signal and providing this optical signal back to the spatial light modulator.

29. An optical add/drop multiplexer according to claim 28, wherein the further optical portion includes a pair of reflective surfaces and lens, one reflective surface arranged at one focal length in relation to one lens and the spatial light modulator, and another reflective surface arranged at a different focal length in relation to another lens and the spatial light modulator.

30. An optical add/drop multiplexer according to claim 29, wherein the one focal length is twice the length of the other focal length.

31. An optical add/drop multiplexer according to claim 28, wherein the further optical portion includes a single reflective surface and lens arrangement.

32. An optical add/drop multiplexer according to claim 31, wherein the spatial light modulator receives the optical input signal and the optical signal to be added to the optical input signal along one optical path, provides selected input channels from each signal back to the optical arrangement, reflects remaining input channels of each signal to the single reflective surface and lens arrangement, and provides the one or more channels dropped from the optical input signal containing the remaining input channels along a second optical path back to the optical arrangement.

33. An optical add/drop multiplexer according to claim 28, wherein the further optical portion includes a single reflective surface and lens arrangement.

34. An optical add/drop multiplexer according to claim 33, wherein the spatial light modulator receives the optical input signal from a first optical portion and the optical signal to be added to the optical input signal from a second optical portion, provides selected input channels from each signal along one optical path back to the second optical portion, reflects remaining input channels of each signal to the single reflective surface and lens arrangement, and provides in the one or more channels dropped from the optical input signal containing the remaining input channels along a second optical path back to the first optical portion.

35. An optical add/drop multiplexer according to claim 12, wherein the one or more optical portions include one or more optical PDL mitigating devices for minimizing polarization dependence loss (PDL).

36. An optical add/drop multiplexer according to claim 35, wherein one optical PDL mitigating device is arranged between a waveguide and a grating in the optical arrangement, and another optical PDL mitigating device is arranged between a grating and the spatial light modulator.

37. An optical add/drop multiplexer according to claim 35, wherein the one or more optical PDL mitigating devices include a pair of optical PDL mitigating devices.

38. An optical add/drop multiplexer according to claim 35, wherein the one or more optical PDL mitigating devices includes one optical PDL mitigating device having a polarization splitter for splitting each channel into a pair of polarized light beams and a rotator for rotating one of the polarized light beams of each optical channel.

39. An optical add/drop multiplexer according to claim 38, wherein the one or more optical PDL mitigating devices includes another optical PDL mitigating device having a rotator for rotating one of the previously rotated and polarized light beams of each optical channel and a polarization splitter for combining the pair of polarized light beams of each channel.

40. An optical add/drop multiplexer according to claim 35, wherein the one or more optical PDL mitigating devices includes a λ

/4 plate.

41. An optical add/drop multiplexer according to claim 2, wherein the diffraction grating has a low PDL.

42. An optical add/drop multiplexer according to claim 12, wherein the optical arrangement includes a chisel prism having multiple faces for modifying the direction of the optical input signal.

43. An optical add/drop multiplexer according to claim 42, wherein the multiple faces include at least a front face, first and second beveled front faces, a rear face, a top face and a bottom face.

44. An optical add/drop multiplexer according to claim 42, wherein optical light from first or second optical portions passes through one or more faces of the chisel prism, reflects off one or more internal surfaces of the chisel prism, reflects off the spatial light modulator, again reflects off the one or more internal surfaces of the chisel prism, and passes back to the first or second optical portions.

49. An optical add/drop multiplexer according to claim 1, wherein the free optic configuration includes a lens and a grating arranged such that the lens is placed at a distance “

d”

from the grating that is shorter than focal length “

f”

of the lens.

50. An optical add/drop multiplexer according to claim 1, wherein the free optic configuration includes a lens and a grating arranged such that the lens is placed a distance “

d”

from the grating that is longer than focal length “

f”

of the lens.

45. An optical cross-connect including an optical arrangement for receiving two or more optical signals, each optical signal having one or more optical bands or channels, and including a spatial light modulator having a micro-mirror device with an array of micro-mirrors for reflecting the two or more optical signals provided thereon, characterized in that

the optical arrangement comprises a free optic configuration having one or more light dispersion elements for separating the two or more optical signals so that each optical band or channel is reflected by a respective plurality of micro-mirrors to selectively switch the one or more optical bands or channels between the two or more optical signals.

46. An optical interleaver/de-interleaver device including an optical arrangement for receiving two or more optical signals, each optical signal having a respective set of at least one optical band or channel, and including a spatial light modulator having a micro-mirror device with an array of micro-mirrors for reflecting the one or more optical signals provided thereon, characterized in that

the optical arrangement comprises a free optic configuration having one or more light dispersion elements for separating the two or more optical input signals so that each optical band or channel is reflected by a respective plurality of micro-mirrors to selectively either combine two respective sets of the at least one optical band or channel into one optical output signal, or de-combine one set of the at least one optical band or channel into two optical output signals each having a different set of the at least one optical band or channel.

47. A reconfigurable optical add multiplexer comprising an optical arrangement for receiving an optical input signal and an optical add signal, each optical signal having one or more optical bands or channels, and including a spatial light modulator having a micro-mirror device with an array of micro-mirrors for reflecting the one or more optical signals provided thereon, wherein

the optical arrangement comprises a free optics configuration having at least one light dispersion element for separating the optical input signal and the optical add signal so that each optical band or channel is reflected by a respective plurality of micro-mirrors to selectively add the one or more optical bands or channels to an optical input signal.

48. A reconfigurable optical drop multiplexer comprising an optical arrangement for receiving an optical input signal, each optical signal having one or more optical bands or channels, and including a spatial light modulator having a micro-mirror device with an array of micro-mirrors for reflecting the one or more optical signals provided thereon, wherein

the optical arrangement comprises a free optics configuration having at least one light dispersion element for separating the optical input signal and the optical add signal so that each optical band or channel is reflected by a respective plurality of micro-mirrors to selectively drop the one or more optical bands or channels from an optical input signal.